An organic electroluminescence device (hereinafter occasionally simply referred to as organic EL device) using an organic substance is highly expected to serve as an inexpensive full-color display device with large area capable of solid-state lighting, so that it has been developed in many ways. A general organic EL device includes an emitting layer and a pair of opposing electrodes between which the emitting layer is interposed. When an electric field is applied between the electrodes, electrons are injected from a cathode while holes are injected from an anode. Recombination of the electrons with the holes in the emitting layer results in generation of an excited state. When the excited state returns to a ground state, energy is released as light.
Compared with an inorganic light-emitting diode, a typical organic EL device requires a high driving voltage but exhibits low luminescence intensity and luminous efficiency. Further, because of serious property degradation, the typical organic EL device has not been put into practical use. Although a recent organic EL device has been progressively improved, it is still required to further improve the organic EL device in terms of luminous efficiency, lifetime, color reproductivity, etc.
With an improved luminescent material for an organic EL device, the performance of an organic EL device has be progressively improved. In particular, improvement in the color purity of a blue-emitting organic EL device (i.e., shortening of the emission wavelength) is deemed as an important technique which leads to improvement in the color reproductivity of a display.
Examples of a material usable for the emitting layer are an anthracene derivative having dibenzofuran as a substituent as disclosed in Patent Literature 1 (International Publication No. WO 2010/137285). Patent Literature 1 also discloses that an organic EL device using this derivative as a host material is driven with a low voltage and is capable of blue emission with a short wavelength.
However, the efficiency and lifetime of the organic EL device disclosed in Patent Literature 1 are not sufficient and thus need to be further increased so that the organic EL device can be used as a light source for electronic devices such as a lighting device and a display.